Uniformity of N-fertiliser spreading and risk of ground water contamination

The uniformity of fertiliser spreading mainly depends on the evenness of the transversal distribution. During the last few years, more than 300 fertiliser spreaders have been tested on farms. The results have shown big differences between machines (coefficient of variation, CV, between 5 and more than 50%). The spreading homogeneity is linked to spreader features, fertiliser characteristics and user skills. The contamination of ground water by nitrogen depends on the locally applied quantity of fertiliser. Using farm spreading patterns, a simulation of the risk of contamination has been established, based on the increase of typical spreading errors. The risk of ground water contamination is assessed by using curves of residual nitrogen observed under field conditions in Belgium. It is thus possible to determine an acceptable level of fertiliser spreading heterogeneity. Copyright (C) 2002 John Wiley Sons, Ltd.